EN8000 Aqwa Tutorial - Memorial University of...
Transcript of EN8000 Aqwa Tutorial - Memorial University of...
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EN8000 Aqwa Tutorial
Evan Martin April 9th, 2009
Aqwa Suite AQWA-LINE
Diffraction & Radiation
AQWA-FER Frequency domain with irregular waves
AQWA-LIBRIUM Static and dynamic initial stability including mooring lines
AQWA-DRIFT time domain with irregular waves including slow drift
AQWA-NAUT non-linear time domain with regular or irregular waves
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Example Analysis Types Irregular Wave Motions
AQWA-LINE RAO’s
AQWA-FER Spectral analysis Statistical prediction of body motions
Coupled Body Analysis AQWA-LINE
Added Mass & Damping AQWA-FER
Coupling constraints
Regular and Irregular Wave Motion in Time Domain AQWA-LINE
Added Mass & Damping AQWA-NAUT or AQWA-DRIFT
Motion time history
Aqwa Line Assumptions First order motions
Harmonic
Small amplitude
Regular incident wave train Small amplitude compared to its length (i.e. small slope).
Potential Flow Inviscid & Irrotational
No viscous damping
Zero or small forward speed (Fn < 0.3)
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Input Files File name convention: AL<id>.dat
AL – indicates Aqwa-Line analysis <id> – arbitrary file identifier
limited to six characters
.dat – Required file extension ie: Alfrygm.dat
Structure Decks – Sections of the input file corresponding to a
specified input type Cards – Lines of the input file corresponding to a
specific input
Card Descriptions Card Descriptions
Column Numbers
Examples
Input Description
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Restart Stages Specify analysis to perform
Allow analysis to be ran in parts Allow different programs to be used in one analysis
Aqwa-Line Stages Stage 1 (Deck 1 – 5)
Geometry definitions Global parameters
Stage 2 (Decks 6 & 7) Analysis Parameters
Stage 3 (No Inputs) Radiation & Diffraction analysis
Aqwa-Line Inputs Hull Geometry (Decks 1 to 4)
Panels Description
Node Coordinates (Deck 1)
Connectivity (Deck 2)
3 or 4 node panels permitted (TPPL or QPPL)
Guidelines No gaps between panels
Normal must point outwards from the body surface into the fluid
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Aqwa-Line Inputs Hull Geometry
Panels Guidelines (Con’t)
Longest edge of plate shorter than 1/7th of the wave length
Elements should have an aspect ratio of greater than 1/3
Distance from the center of panel to water surface (zs)
zs > 0.000273 * (water depth)
zs > 0.0000132 * (wave length)
Ratio of areas of adjacent plates should be greater than 1/3
Aqwa-Line Inputs Hull Geometry
Masses Hull mass composed of one or more point masses
One Point Mass – Entire ship (CoG)
Multiple Point Masses – Lightship (CoG) & Cargo
Etc.
Point Mass Description Location (Deck 1)
Associated Structure (Deck 2)
Mass (Deck 3)
Mass moment of inertia (Deck 4)
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Aqwa-Line Inputs Global Parameters (Deck 5)
Water Depth Water Density Acceleration Due to Gravity
Wave Frequency (Deck 6) Range selected to represent region where RAO’s and
wave spectra have significant energy Sufficient spacing to adequately describe variation of
hydrodynamic coefficients AQWA-FER will interpolate between specified values if
required
Aqwa-Line Inputs Wave Direction (Deck 6)
All possible directions of subsequent analysis Negative frequency of encounters not premitted
Additional Stiffness (Deck 7) Mooring Lines
Additional Damping (Deck 7) Viscous Roll Damping
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Ferry Example Displacement: 5,760
Tonnes
Design Speed: 8.474 m/s
Center of Gravity 47.93 m aft of FP
4.987 above waterplane
Viscous Roll Damping: 5.85×106 Ns/m
Moments of Inertia Roll: 3.56×108 kgŸm2
Pitch: 4.84×109
Yaw: 4.84×109
Water Depth: 1000 m
Frequencies: 0.25 to 2.2 rad/s
Input File Header Deck 0 – Preliminary Deck
Job Card User ID
Program – (Aqwa Line)
Title User description of the file
Options REST – Indicates a restart
GOON – Ignore modeling rule violations
END – Required at end of options
Restart Stages
JOB 0001 LINE TITLE LABRADOR FERRY OPTIONS LDOP REST END RESTART 1 1
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Geometry Limitations Wave Lengths: 12.7 to 1530m
Longest Edge: < 1/7th of the wave length = 1.82m
Depth below surface (zs): > 0.000273 * (water depth) = 0.546m > 0.0000132 * (wave length) = 0.0202m
For rectangular panel, minimum angle with surface asin(2*0546/1.82) = 37˚
Panel Layout
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Hull Geometry Deck 1 – Coordinate Positions
01 COOR 01 1 0.000 0.000 0.000 01 2 -2.000 0.000 -0.970
... 01 969 -100.320 3.302 0.000 END019999 -47.932 0.000 4.987
02 ELM1 02SYMX 02TPPL DIFF (1)(1,1)(2,1)(3,1)
... 02QPPL DIFF (1)(11,1)(16,1)(17,1)(12,1)
... END02PMAS (1)(9999)(1)(1) 02 FINI
Deck 2 – Coordinate Positions
Student Activity Based on printouts from the Aqwa reference
manual “AQWA Reference.chm”, write the input for the selected deck. Use the inputs given below
Pay attention to the number of spaces required
Displacement: 5,760 Tonnes
Design Speed: 8.474 m/s
Center of Gravity 47.93 m aft of FP 4.987 above waterplane
Viscous Roll Damping: 5.85×106 Ns/m
Moments of Inertia Roll: 3.56×108 kgŸm2 Pitch: 4.84×109 Yaw: 4.84×109
Water Depth: 1000 m
Frequencies: 0.25 to 2.2 rad/s
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Student Activity Deck 3 – Material Properties
Ships Displacement 03 MATE END03 1 575.876E4
04 GEOM END04PMAS 1 3.5625E8 0.0 0.0 4.8440E9 0.0 4.8440E9
Deck 4 – Geometric Properities Mass Moments of Inertia
Student Activity Deck 5 – Global Parameters
Water Depth Water Density Acceleration Due to Gravity
05 GLOB 05DPTH 1000.0 05DENS 1025.0 END05ACCG 9.806
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Student Activity Deck 6 – Frequencies and Directions
Wave Frequencies Wave Heading
Forward Speed
06 FDR1 06FREQ 1 3 0.250 0.300 0.350 06FREQ 4 6 0.400 0.450 0.500
... 06FREQ 28 30 2.100 2.150 2.200 06DIRN 1 1 180.0 END06FWDS 8.474
Note: Aqwa only allows one direction to be used when a forward speed is given
Student Activity Deck 7 – Frequency Dependent Parameters
Roll Damping Position of COG relative to waterline
07 WFS1 07FIDD 5.85E6 END07ZCGE 4.987
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Analysis Completed Input Files
alfrygm.dat alfryhd.dat
Run Commands C:\aqwa\utils\aqwa57a LINE frygm
copy alfrygm.res alfryhd.res C:\aqwa\utils\aqwa57a LINE fryhd
Example Output File Alfryh2d180.lis
Plot of RAOs
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Plot of Phase Angles